1. Field of the Invention
The present invention relates to a method of filtering overlay data by field, and more particularly, to a method of filtering overlay data by field for generating modified exposure parameters.
2. Description of the Prior Art
In semiconductor manufacturing processes, in order to transfer an integrated circuit onto a semiconductor wafer, the integrated circuits from a database are first designed as a layout pattern and a photomask is then manufactured according to the layout pattern. Patterns on the photomask may then be able to be transferred to the semiconductor wafer. The steps mentioned above may be regarded as a photolithographic process. The layout pattern has to be extremely accurate for forming delicate integrated circuits so as to align with the patterns of the previous and following steps.
The overlay errors between different patterned layers might occur for many reasons, such as the alignment accuracy of the exposure apparatus, wafer warpage, and influence from other manufacturing processes. The overlay errors have to be monitored for quality control and being used to modify the exposure parameters and/or find out the cause of the overlay error.